There has been considerable development in the construction and operation of smoke detectors of various types for emitting a warning or an alarm signal when smoke reaches a density indicative of a fire. One of the types of smoke detector alarms includes the use of light responsive means, such as photocells, for receiving a light beam emanating from a light source in the detector housing and reflected off smoke particles in a smoke chamber to the photocell. Since the purpose of a smoke detector is to be immediately activated in the event of a fire at any time of the day or night, it is necessary that such a smoke detector be readily tested for its operability and warning function at suitable regular intervals. Inoperability of smoke detector at the time of a fire destroys the entire purpose of the smoke detector. Therefore, it is imperative that a test means be provided for smoke detectors to rapidly, conveniently and easily test operability of the detector.
In smoke detectors which respond to a reflected light beam from smoke particles in the smoke chamber, testing could be accomplished by creating a supply of smoke beneath the detector device until the smoke entered the smoke chamber and the preselected smoke density was reached in the chamber to activate the alarm. If the alarm was not activated, it would be presumed that the alarm device was inoperable. However, inoperability of the smoke detector might be caused by several factors, including density of the smoke in the chamber, intensity of the light beam source, responsiveness of the photocell, and the electrical circuitry which was connected to the photocell and electrically actuated an alarm signal.
Prior proposed test means for smoke detectors of light responsive type have included the use of sevral photocells, a supervisory control circuit to activate the alarm upon failure of electrical components in the smoke detector circuit, and the use of a test probe means inserted in the smoke chamber, the test probe means having a reflective equivalence with respect to the light source and photocell of predetermined concentrations of smoke in the smoke chamber for specified depths of insertion of the probe into the smoke chamber, see U.S. Pat. No. 3,585,621. Such prior proposed testing means known to us did not provide a means for quickly and rapidly determining whether the smoke device was operable by making such test without entering the smoke chamber and by manually moving an external arm a preselected distance.